Can replacing a cat make my Boxster sound better?
 

Ever since I bought my 2003 Boxster last year I've thought it sounded a bit "tinny". I've never owned one before so I accepted it and thought perhaps I might look into a replacement exhaust unit at some time in the future. However last year soon after delivery I popped a check engine light and it was diagnosed as a bad cat. We tried changing the O2 sensor but no joy. It rested over the winter but with the arrival of spring she is back on the road. The light was off for about 17 miles and then it was back on again.

Took it my local indie shop and he was able to get me a cat pulled from someone who did an upgrade. I picked up the car with the new cat installed this afternoon. It could be wishful thinking but I swear that the exhaust note is deeper and throatier now. All I was expecting was for the CE light to be off and to stay off. I've only put about 15 miles on the car so far but it truly seems to sound different, and in a good way.

My question, can replacing a cat change the way the car sounds and if so, how come?

Thanks.

A.

So you changed out your defective stock primary cats with a pair of used stock cats from your indie. I wouldn't think that would change the tone. Maybe you just miss your boxster? :eek: However, replacing your cats with a test/delete pipe will make it growl more

A cat on my son's Miata went bad and it did sound bad, maybe tinny is a good word. We replaced it and the tinny went away :)

If your cat was clogged up, yeah I could see a change of sound.

I would also be very curious as to what caused the cat to fail. How many miles on the car? Any smoke coming out of the tail pipe?

My cats went bad on my 2003 Boxster S. I know why. My AOS was slowly pumping oil into my intake system, it didn't blow like most do on people and turns their car into a mosquito fog machine with all the oil being dumped into the intake system. Every now and then I'd get a puff of smoke at start up, that would usually occur if I turned the engine on briefly and then turned it off, like moving my car from the driveway into the garage, sometimes the next start up would blow out a puff of smoke.

I actually didn't know my AOS was slowly dumping oil into the air intake system until I went to upgrade my air intake system and found oil in the distribution T to the plenums and in the hose going to the AOS.

I have to spend some more time listening to it but I am almost certain that something just sounds different. IT now sounds more like various videos and TV shows I have seen about Boxsters. Not complaining by any means. Just curious.

A.

The car has just over 40,000. I never noticed smoke before. I did see some when I picked it up today and will be keeping an eye on that. I have started it a few times since I picked it up and have not seen the smoke anymore so far but I've only have it for a few hours now.

I do not know what caused the failure but it was consistent and multiple resets did not keep it from coming back each time. I am truly hoping this finally keeps the darn CE light off.

A.

One word:

De-snorkle

40k miles is very low for a cat to fail without another issue causing it. Easy way to check and see if you AOS is pumping oil into your intake. Take off the tube I have circled in red, it comes directly from the AOS, check it for oil.

http://i59.tinypic.com/2enopxy.jpg

If there is just a slight bit of oil that might be normal, not sure on that though, but if there is a decent amount of oil I would look into replacing the AOS before it mucks up your cats.

EDIT: Handle that hose gently, even though it was originally made flexible, mine was very brittle and broke when I was moving it out of the way during my intake upgrade.

Good point. I just today watched a YouTube video on this exact thing:

https://www.youtube.com/watch?v=ipkQUKkUcJk

Thanks.

A.

Nice, you're researching. :cheers:

That's a good video, but on our 2003 Boxsters the AOS is a bit different then the one he shows in the video. It's actually very easy to remove and install the AOS on our cars. Ours look like this one.

http://c1552172.r72.cf0.rackcdn.com/524148_x800.jpg

Thanks. I checked my records and a new AOS was installed last October. I've driven less than 1500 miles since then. I am not comfortable pulling parts off the engine to look at that so I may have the shop take a look the next time I have it back for service. I am up for an emission check in August.

A.

If your car never dumps out smoke you're more then likely good. The previous failed AOS probably mucked up that cat. I also forgot about the removing the oil cap to check on the vacuum pressure, you could do that yourself.

Isn't Timco going to offer his comments about cats ;)?

Joe, I was about to say this is the most civilized cat conversation we have ever had on the forum.

Give it time... :D